1. Field of the Invention
This invention generally relates to an ink sheet cassette containing therein a quantity of ink sheet for use in a thermal transfer printer, and in particular to an ink sheet/recording paper cassette containing therein both a roll of ink sheet and a roll of recording paper for use in a thermal transfer printer as detachably mounted therein.
2. Description of the Prior Art
Recently, as an image recording apparatus for use in a facsimile or the like, an image recording apparatus using a thermal print head has been widely used and various such image recording apparatuses have been marketed because of simplicity in structure and mechanism and low at cost. A typical prior art image recording apparatus 1 of this type is schematically shown in FIG. 18 and it includes a main housing la which houses therein a roll of ink sheet 2, a roll of recording paper 3, a guide roller 4, a separation roller 5, a take-up spool 6, a thermal print head 7, a platen roller 8 and a cutter unit 9. As the ink sheet 2, use is, for example, made of an ink sheet which includes a base sheet of polyester of a few microns thick and a thermally transferable ink layer formed on the base sheet, and the ink sheet 2 normally has a width larger than that of the recording paper 3 and initially wound around a supply spool 2a. The roll of ink sheet 2 is mounted on a support structure (not shown) and it is wound from the roll and wound around the take-up spool 6 after moving past the guide roller 4 and the separation roller 5.
The support structure of the roll of ink sheet 2 is provided with a back tension mechanism (not shown) so that a predetermined tension is maintained in that portion of the ink sheet 2 which has been unwound from the roll to thereby prevent the occurrence of creases in the ink sheet 2. The take-up spool 6 is coupled to a take-up mechanism (not shown) and it takes up the ink sheet 2, which has been presented for recording, in association with the rotation of the platen roller 8. The take-up mechanism is provided with a one-way clutch mechanism which serves to take up the ink sheet 2 when the platen roller 8 is driven to rotate in the direction for supplying the recording paper 3 and on the other hand which also serves to prevent taking up of the ink sheet 2 when the platen roller 8 rotates in the direction for moving the recording paper 3 back toward the thermal print head 7. The recording paper 3 is typically a sheet of plain paper which is initially provided in the form of a roll as wound around a shaft 3a which in turn is rotatably supported in position by means of a support structure (not shown). The recording paper 3 is unwound from the roll and is supplied between the thermal print head 7 and the platen roller 8 as guided by the guide roller 4, together with the ink sheet 2.
As well known in the art, the thermal print head 7 is provided with a plurality of heat-producing (or resistor) elements arranged in the form of a single array at a predetermined pitch (not shown), which are selectively activated to produce a heat pattern in accordance with image information supplied from a control unit, whereby the ink layer of the ink sheet 2 is selectively melted and then transferred to the recording paper 3 in contact with the ink sheet 2 to effect recording line by line while the recording paper 3 is in contact with the ink sheet 2 as sandwiched between the thermal print head 7 and the platen roller 8. Upon completion of thermal transfer recording, the ink sheet 2 is separated away from the recording paper 3 by means of the separation roller 5 which is located downstream of the thermal print head 7 with respect to the direction of advancement of the ink sheet 2 and also the recording paper 3, so that the ink sheet 2 is wound around the take-up spool 6 and on the other hand the recording paper 3 advances into the cutter unit 9. Thus, the recording paper 3 is cut into a sheet of predetermined size by the cutter unit 9 and the thus cut sheet of recording paper 3 is discharged out of the present image recording apparatus.
Each of the ink sheet 2 and the recording paper 3 is provided with an end mark at its end and these end marks may be detected by end mark sensors (not shown) provided in the image recording apparatus. It should be noted that also provided in the structure shown in FIG. 18 are paper guide plates for guiding the advancement of the recording paper 3 along a predetermined paper transportation path defined in the image recording apparatus; however, no reference numerals are assigned to these paper guide plates in FIG. 18. Upon cutting of the recording paper by the cutter unit 9, the platen roller 3 is typically driven to rotate in the reversed direction to cause the recording paper 3 move back toward the thermal print head 7 over a predetermined length to thereby set the leading margin at around 2 mm so as to minimize the waste of recording paper 3.
In such a typical prior art thermal transfer type recording apparatus, the ink sheet 2 and the recording paper 3 are typically mounted in position separately, and thus replacement of either one of both of these components tends to be complicated in procedure and thus difficult to carry out. That is, when it is desired to carry out replacement of ink sheets 2, the supply spool 2a and the take-up spool 6 are detached from the support structure and a new roll of ink sheet 2 is set in position in the support structure, whereby the new ink sheet 2 must be passed around the guide roller 4 and the separation roller 5 and the take-up spool 6 to which the leading end of the ink sheet 2 is fixedly attached must be set in position in the take-up mechanism. In the case where the recording paper 3 is to be replaced with a new roll, the shaft 3a carrying no more recording paper 3 is removed from the support structure and a new roll of recording paper 3 is set in position in the support structure, followed by the steps of unwinding the leading end of the recording paper 3, passing the leading end around the guide roller 4 and inserting the leading end through the cutter unit 9. In particular, when mounting a new ink sheet 2 in position, if the operator touches the ink layer of the ink sheet 2 by a hand or fingers, the ink layer may be locally removed while the hand or fingers of the operator get stained. Besides, since the ink sheet 2 is normally extremely thin, creases may be formed in the unwound portion of the ink sheet 2 when the ink sheet 2 is not properly set in position.
If the ink layer of the ink sheet 2 is locally removed or creases are present in the unwound portion of the ink sheet 2 as described above, image information may be partially lost when recorded with such an ink sheet 2 or the resulting recorded image may become poor in quality. For this reason, an extremely careful attention is required in handling the ink sheet 2 of this type of recording apparatus. Moreover, it is required to provide a separate end detecting sensor for each of the ink sheet 2 and the recording paper 3, so that the overall size of the recording apparatus is hindered to make compact in size and it also hinders to lower the overall cost. Besides, it is also required to provide an end mark in each of the ink sheet 2 and the recording paper 3 separately so that manufacture of such an ink sheet 2 and recording paper 3 tends to become expensive since an extra step of providing an end mark is required for each of ink sheet 2 and recording paper 3.
Furthermore, plain paper and heat-sensitive paper for use as the recording paper 3 look similar, so that, for example, when switching from a thermal transfer recording mode using plain paper to a direct recording mode using heat-sensitive paper, the operator may often forget to replace the recording paper 3 of plain paper with heat-sensitive recording paper after removal of the ink sheet 2. The operator may also mount plain paper in position while believing it to be heat-sensitive paper. In such a case, image information is not recorded and could be lost.